Optical touch screens

ABSTRACT

A lens for placement opposite a diode in an optical touch sensor, including an upper portion including an upper refractive surface located nearer to the diode, and an upper reflector located further from the diode, the upper reflector being curved in two dimensions and cut horizontally by a top horizontal plane of the lens, and a lower portion, coplanar with the diode, including a lower refractive surface located nearer to the diode, and a lower reflector located further from the diode, the lower reflector being curved in the two dimensions and cut horizontally by a bottom horizontal plane of the lens, wherein the upper and the lower reflector are symmetrical and vertically aligned, and wherein non-collimated light reflected by the lower reflector onto the upper reflector is partially collimated in the two dimensions by the lower reflector and further collimated in the two dimensions by the upper reflector.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of PCT Patent Application No.PCT/US14/40579, entitled OPTICAL TOUCH SCREENS, and filed on Jun. 3,2014 by inventors Robert Pettersson, Per Rosengren, Erik Rosengren,Stefan Holmgren, Lars Sparf, Richard Berglind, Thomas Eriksson, KarlErik Patrik Nordstrom, Gunnar Martin Fröjdh, Xiatao Wang and RemoBehdasht.

This application is a continuation-in-part of U.S. patent applicationSer. No. 13/052,511, entitled LIGHT-BASED TOUCH SCREEN WITHSHIFT-ALIGNED EMITTER AND RECEIVER LENSES, and filed on Mar. 21, 2011 byinventors Magnus Goertz, Thomas Eriksson, Joseph Shain, Anders Jansson,Niklas Kvist, Robert Pettersson, Lars Sparf and John Karlsson.

PCT Patent Application No. PCT/US14/40579 claims priority benefit from:

-   -   U.S. Provisional Patent Application No. 61/830,671, entitled        MULTI-TOUCH OPTICAL TOUCH SCREENS WITHOUT GHOST POINTS, and        filed on Jun. 4, 2013 by inventors Erik Rosengren, Robert        Pettersson, Lars Sparf and Thomas Eriksson;    -   U.S. Provisional Patent Application No. 61/833,161, entitled        CIRCULAR MULTI-TOUCH OPTICAL TOUCH SCREENS, and filed on Jun.        10, 2013 by inventors Richard Berglind, Erik Rosengren, Robert        Pettersson, Lars Sparf, Thomas Eriksson, Gunnar Martin Fröjdh        and Xiatao Wang;    -   U.S. Provisional Patent Application No. 61/919,759, entitled        OPTICAL TOUCH SCREENS WITH TOUCH-SENSITIVE BORDERS, and filed on        Dec. 22, 2013 by inventors Remo Behdasht, Erik Rosengren, Robert        Pettersson, Lars Sparf, Thomas Eriksson;    -   U.S. Provisional Patent Application No. 61/911,915, entitled        CIRCULAR MULTI-TOUCH OPTICAL TOUCH SCREENS, and filed on Dec. 4,        2013 by inventors Richard Berglind, Erik Rosengren, Robert        Pettersson, Lars Sparf, Thomas Eriksson, Gunnar Martin Fröjdh        and Xiatao Wang;    -   U.S. Provisional Patent Application No. 61/923,775, entitled        MULTI-TOUCH OPTICAL TOUCH SCREENS WITHOUT GHOST POINTS, and        filed on Jan. 6, 2014 by inventors Per Rosengren, Stefan        Holmgren, Erik Rosengren, Robert Pettersson, Lars Sparf and        Thomas Eriksson; and    -   U.S. Provisional Patent Application No. 61/950,868, entitled        OPTICAL TOUCH SCREENS, and filed on Mar. 11, 2014 by inventors        Karl Erik Patrik Nordstrom, Per Rosengren, Stefan Holmgren, Erik        Rosengren, Robert Pettersson, Lars Sparf and Thomas Eriksson.

U.S. patent application Ser. No. 13/052,511 claims priority benefitfrom:

-   -   U.S. Provisional Patent Application No. 61/379,012, entitled        OPTICAL TOUCH SCREEN SYSTEMS USING REFLECTED LIGHT, and filed on        Sep. 1, 2010 by inventors Magnus Goertz, Thomas Eriksson, Joseph        Shain, Anders Jansson, Niklas Kvist and Robert Pettersson;    -   U.S. Provisional Patent Application No. 61/380,600, entitled        OPTICAL TOUCH SCREEN SYSTEMS USING REFLECTED LIGHT, and filed on        Sep. 7, 2010 by inventors Magnus Goertz, Thomas Eriksson, Joseph        Shain, Anders Jansson, Niklas Kvist and Robert Pettersson; and    -   U.S. Provisional Patent Application No. 61/410,930, entitled        OPTICAL TOUCH SCREEN SYSTEMS USING REFLECTED LIGHT, and filed on        Nov. 7, 2010 by inventors Magnus Goertz, Thomas Eriksson, Joseph        Shain, Anders Jansson, Niklas Kvist, Robert Pettersson and Lars        Sparf.

U.S. patent application Ser. No. 13/052,511 is a continuation-in-partof:

-   -   U.S. patent application Ser. No. 12/371,609, now U.S. Pat. No.        8,339,379, entitled LIGHT-BASED TOUCH SCREEN, and filed on Feb.        15, 2009 by inventors Magnus Goertz, Thomas Eriksson and Joseph        Shain;    -   U.S. patent application Ser. No. 12/760,567, entitled OPTICAL        TOUCH SCREEN SYSTEMS USING REFLECTED LIGHT, and filed on Apr.        15, 2010 by inventors Magnus Goertz, Thomas Eriksson and Joseph        Shain;    -   U.S. patent application Ser. No. 12/760,568, entitled OPTICAL        TOUCH SCREEN SYSTEMS USING WIDE LIGHT BEAMS, and filed on Apr.        15, 2010 by inventors Magnus Goertz, Thomas Eriksson and Joseph        Shain.

U.S. patent application Ser. No. 12/760,567 claims priority benefit fromU.S. Provisional Patent Application No. 61/169,779, entitled OPTICALTOUCH SCREEN, and filed on Apr. 16, 2009 by inventors Magnus Goertz,Thomas Eriksson and Joseph Shain.

The contents of all of these applications are hereby incorporated byreference in their entireties.

FIELD OF THE INVENTION

The field of the present invention is light-based touch screens.

BACKGROUND OF THE INVENTION

Many consumer electronic devices are now being built with touchsensitive surfaces (track pad or touch screen), for use with finger orstylus touch user inputs. These devices range from small screen devicessuch as mobile phones and car entertainment systems, to mid-size screendevices such as notebook computers, to large screen devices such ascheck-in stations at airports.

In computing, multi-touch refers to a touch sensing surface's ability torecognize the presence of two or more points of contact with thesurface. This plural-point awareness is often used to implement advancedfunctionality such as pinch to zoom or activating predefined programs(Wikipedia, “multi-touch”). The Windows 8 operating system fromMicrosoft Corporation requires a touch screen supporting a minimum of5-point digitizers. WINDOWS® is a registered trademark of MicrosoftCorporation.

The present invention relates to light-based touch sensitive surfaces.Light-based touch sensitive surfaces surround the surface borders withlight emitters and light detectors to create a light beam grid above thesurface. An object touching the surface blocks a corresponding portionof the beams.

Reference is made to FIG. 1, which is a diagram of a prior art,light-based touch screen having 16 LEDs and 16 PDs. Screen 801 in FIG. 1is surrounded by emitters 101 along two edges and photodiode (PD)receivers 201 along the remaining two edges, which together enable alattice of light beams 300 covering the screen.

Light-based touch detection systems are unable to accurately recognizemany instances of two or more points of contact with the surface.Reference is made to FIGS. 2 and 3, which are illustrations of instancesof ambiguous multi-touch detections in prior art touch screens. FIGS. 2and 3 show different instances of two, diagonally opposed touches 901and 902 that are ambiguous vis-à-vis the light grid of FIG. 1. As shownin FIGS. 2 and 3, the same light beams are blocked in both instances.

There is further ambiguity when more than two objects touch the screensimultaneously. Reference is made to FIGS. 4 and 5, which areillustrations of instances of ghosted touches in prior art touchscreens. The two-touch cases shown in FIGS. 2 and 3 are also ambiguousvis-á-vis the three-touch case, 901-903, shown in FIG. 4, and vis-à-visthe four-touch case, 901-904, shown in FIG. 5. In each of the casesillustrated in FIGS. 2-5, row and column PDs a-h show an absence oflight in the same locations. The ambiguity illustrated in FIGS. 4 and 5is caused by “ghosting”, which refers to an effect where the shadow of afirst object obscures a second object and prevents the second objectfrom being detected.

Light-based touch screens have many advantages over other touch sensortechnologies such as capacitive and resistive solutions. Inter alia,light-based touch screens enable lower bill-of-materials cost thancapacitive solutions, especially for large screens. Light-based touchscreens are also superior to capacitive and resistive solutions in thata light-based touch screen does not require an additional physical layeron top of the screen that impairs the screen image. This is an importantadvantage for devices employing reflective screens where the brightnessof the screen image depends on reflected light, rather than a backlight.Reference is made to U.S. Pat. No. 8,674,966 for ASIC CONTROLLER FOR ALIGHT-BASED TOUCH SCREEN, incorporated herein by reference in itsentirety, which teaches faster scan rates for light-based touch screensthan are available using prior art capacitive screens. It would beadvantageous to provide a light-based touch screen that is operative todetect multi-touch gestures and that is compatible with the requirementsof the Windows 8 operating system.

One drawback of prior art light-based touch screens is the need toaccommodate the numerous light emitters and light detectors along allfour edges of the screen. This requirement makes it difficult to insertlight-based touch detection into an existing electronic device withoutsignificantly changing the layout of the device's internal components.It would be advantageous to reduce the number of components required andto enable placing them in a limited area rather than surrounding theentire screen. Reducing the total number of light emitters and lightdetectors required has the added benefit of reducing thebill-of-materials (BOM).

SUMMARY

Embodiments of the present invention provide unambiguous multi-touchdetection based on blocked light beams. Other embodiments of the presentinvention provide 2D touch detection using a one-dimensional array oflight emitters along only one edge of the screen and an opposite arrayof light detectors along the opposite edge of the screen.

There is thus provided in accordance with an embodiment of the presentinvention a rectangular arrangement of light emitters and lightdetectors, where light emitters are arranged along two adjacent edges ofthe rectangular arrangement and light detectors are arranged along thetwo remaining edges. Light from each emitter is detected by a pluralityof the detectors. Each beam from an emitter to a detector traverses aplurality of screen pixels. A table stored in computer memory lists, foreach beam, all of the pixels that lie in the beam's path. For eachblocked beam, all of the pixels in the beam's path are marked asblocked; and for each non-blocked beam, all of the pixels in the beam'spath are marked as unblocked. This creates a map with three types ofpixels: fully blocked, fully unblocked and partially blocked. Apartially blocked pixel is traversed by several beams, only some ofwhich are blocked. A fully blocked pixel is traversed by several beams,all of which are blocked. The fully blocked pixels correspond to thetouch locations. The system then connects adjacent blocked pixels toconstruct blobs of contiguous blocked pixels. Each blob, or set ofcontiguous blocked pixels, is treated as a single touch location.

There is additionally provided in accordance with an embodiment of thepresent invention a touchscreen featuring a row of light emitters alongthe bottom edge of the screen and a row of light detectors along the topedge of the screen. Each light emitter projects a very wide beam that isdetected by all of the light detectors. The x-coordinate of an objecttouching the screen corresponds to a blocked beam that runs parallel tothe side edges of the screen. The y-coordinate is determined byidentifying the intersections between diagonal blocked beams.

There is further provided in accordance with an embodiment of thepresent invention a lens for placement opposite a diode in an opticaltouch sensor, including an upper portion including an upper refractivesurface located nearer to the diode, and an upper reflector locatedfurther from the diode, the upper reflector being curved in twodimensions and cut horizontally by a top horizontal plane of the lens,and a lower portion, coplanar with the diode, including a lowerrefractive surface located nearer to the diode, and a lower reflectorlocated further from the diode, the lower reflector being curved in thetwo dimensions and cut horizontally by a bottom horizontal plane of thelens, wherein the upper and the lower reflector are symmetrical andvertically aligned, and wherein non-collimated light reflected by thelower reflector onto the upper reflector is partially collimated in thetwo dimensions by the lower reflector and further collimated in the twodimensions by the upper reflector.

In cases where the lens' viewing angle of the diode is large, the heightof the lens between the top and bottom horizontal planes is less thanthe height required for a curved reflector, cut vertically by a rearvertical backplane of the lens, to partially collimate and furthercollimate the non-collimated light.

There is yet further provided in accordance with an embodiment of thepresent invention a method a method for calculating multiple touchlocations on a screen including activating a plurality of emitters anddetectors around the perimeter of a screen, wherein eachemitter-detector pair corresponds to a light beam crossing the screen,from among a plurality of such light beams, and wherein some of thelight beams are blocked by one or more objects touching the screen,providing a look-up table listing, for each light beam from theplurality of light beams, other light beams from the plurality of lightbeams, that intersect that light beam, and their respective points ofintersection, (a) identifying a first blocked light beam, (b) accessingthe look-up table to identify a second blocked light beam thatintersects the first blocked beam, (c) accessing the look-up table toidentify intersection points of other blocked light beams that neighborthe intersection point of the thus-identified first and second blockedbeams, (d) repeating operations (b) and (c) until all neighboringintersections points of blocked beams have been identified, and groupthe thus-identified neighboring intersections as a single touch point,and (e) repeating operations (a)-(d) for remaining blocked light beamsthat were not yet grouped at operation (d).

There is moreover provided in accordance with an embodiment of thepresent invention a method for calculating multiple touch locations on ascreen including activating a plurality of emitters and detectors aroundthe perimeter of a screen, wherein each emitter-detector paircorresponds to a light beam crossing the screen, from among a pluralityof such light beams, and wherein some of the light beams are blocked byone or more objects touching the screen, identifying the screen as aninitial touch candidate region, for each candidate region: (a)identifying an unblocked light beam crossing that candidate region, (b)dividing that candidate region into multiple candidate regions,separated by the thus-identified unblocked light beam, and (c) repeatingoperations (a) and (b) for all unblocked beams, and designating thecandidate regions whose sizes are larger than a minimum size, as beingunique touch locations.

There is additionally provided in accordance with an embodiment of thepresent invention a method a method for calculating a touch location ona screen including providing a plurality of emitters and detectorsaround the perimeter of a screen, wherein each emitter-detector paircorresponds to a wide light beam crossing the screen, from among aplurality of wide light beams, activating a screen scan pairing eachemitter with an opposite detector, (a) identifying those wide lightbeams, from the plurality of wide light beams, that are being blocked byan object touching the screen, (b) identifying an area of intersectionbetween substantially perpendicularly oriented ones of the blocked widebeams identified at operation (a), (c) identifying additional blockedwide beams that cross the area of intersection identified at operation(b), (d) determining a degree of blockage for each additional blockedwide light beam identified at operation (c), (e) identifyingtwo-dimensional shapes formed by the intersection of each additionalblocked wide light beam identified at operation (c) with the blockedwide light beams identified at operation (a), and (f) calculating aweighted average of the centers-of-gravity of the thus-identifiedtwo-dimensional shapes, wherein each center-of-gravity's weight in thesum corresponds to its respective degree of blockage determined atoperation (c).

There is further provided in accordance with an embodiment of thepresent invention a circular touch sensor including a housing, a surfacemounted in the housing, including a circular portion exposed to receivetouch input, a plurality of light detectors mounted in the housing alonga semicircular contour corresponding to a half of the circular portion,wherein an angular pitch between neighboring detectors is constant, aplurality of light emitters mounted in the housing along an oppositesemicircular contour corresponding to the opposite portion of thecircular portion, and arranged in groups such that an angular pitchbetween neighboring emitters within each group is θ, and such that anangular pitch between nearest emitters in different groups is θ+α, whereα is positive, and a processor connected to the emitters and to thedetectors, for synchronously co-activating emitter-detector pairs, andconfigured to calculate a two-dimensional location of an object touchingthe circular portion, based on outputs of the detectors.

There is yet further provided in accordance with an embodiment of thepresent invention a circular touch sensor including a housing, a surfacemounted in the housing including a circular portion exposed to receivetouch input, a plurality of light emitters mounted in the housing alonga semicircular contour corresponding to half of the circular portion,wherein an angular pitch between neighboring emitters is constant, aplurality of light detectors mounted in the housing along an oppositesemicircular contour corresponding to the opposite half of the circularportion, and arranged in groups such that an angular pitch betweenneighboring detectors within each group is θ, and such that an angularpitch between nearest detectors in different groups is θ+α, where α ispositive, and a processor connected to the emitters and to thedetectors, for synchronously co-activating emitter-detector pairs, andconfigured to calculate a two-dimensional location of an object touchingthe circular portion, based on outputs of the detectors.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be more fully understood and appreciated fromthe following detailed description, taken in conjunction with thedrawings in which:

FIG. 1 is a diagram of a prior art, light-based touch screen having 16LEDs and 16 PDs;

FIGS. 2 and 3 are illustrations of instances of ambiguous multi-touchdetections in prior art touch screens;

FIGS. 4 and 5 are illustrations of instances of ghosted touches in priorart touch screens;

FIG. 6 is an illustration of a network of intersecting light beams in atouch screen system, in accordance with an embodiment of the presentinvention;

FIG. 7 is an illustration of a network of intersecting light beamsdetecting five touch points in a touch screen system, in accordance withan embodiment of the present invention;

FIG. 8 is a flow chart describing a first method for identifying touchlocations, in accordance with an embodiment of the present invention;

FIG. 9 is a flow chart describing a second method for identifying touchlocations, in accordance with an embodiment of the present invention;

FIG. 10 is an illustration of neighboring intersections used by themethod of FIG. 9, in accordance with an embodiment of the presentinvention;

FIG. 11 is an illustration of a network of connected blocked beams usedto locate a touch object, in accordance with an embodiment of thepresent invention;

FIG. 12 is an illustration of five identified touch objects identifiedby a touch screen, in accordance with an embodiment of the presentinvention;

FIGS. 13-18 are illustrations of an alternative method for determiningtouch locations, whereby portions of a large, candidate touch area areexcluded based on unblocked thin light beams, in accordance with anembodiment of the present invention;

FIG. 19 is an illustration of five circles indicating areas though whichno beams pass due to touch objects, in accordance with an embodiment ofthe present invention;

FIG. 20 is a graph tracking the number of separate touch candidate areasas a function of the number of unblocked beams, in accordance with anembodiment of the present invention;

FIGS. 21 and 22 are simplified illustrations of a partially blocked widebeam, that illustrate effects of where a blocking object is placed, inaccordance with an embodiment of the present invention;

FIG. 23 is a simplified exemplary illustration of iso-curves across thewidth of a wide light beam, in accordance with an embodiment of thepresent invention;

FIGS. 24-30 are simplified illustrations of a method of touch locationdetermination, whereby portions of a large, candidate touch area areexcluded based on unblocked, and partially blocked, wide light beams, inaccordance with an embodiment of the present invention;

FIG. 31 is a simplified illustration of a partially blocked wide beamthat extends between two adjacent screen edges, in accordance with anembodiment of the present invention;

FIGS. 32-34 are simplified drawings of an object being detected, inaccordance with another method of the present invention, utilizing widelight beams;

FIG. 35 is a flowchart for a method of eliminating ghost touches, inaccordance with an embodiment of the present invention;

FIG. 36 is a simplified drawing of a lens that distributes beams acrossmany angles, in accordance with an embodiment of the present invention;

FIG. 37 is a simplified figure of four different fields of view that areall focused on a single diode, in accordance with an embodiment of thepresent invention;

FIG. 38 is a simplified illustration of the four fields of view of FIG.37 as viewed from above, in accordance with an embodiment of the presentinvention;

FIGS. 39 and 40 are simplified illustrations of two beams from oneemitter to two respective PDs, in accordance with an embodiment of thepresent invention;

FIGS. 41-43 are simplified illustrations of an arrangement ofcomponents, light guides, PCB and screen in a device, in accordance withan embodiment of the present invention;

FIGS. 44 and 45 are simplified illustrations of a light guide, inaccordance with an embodiment of the present invention;

FIG. 46 is a simplified illustration of how microstructures correct theproblem of gaps in the light field, in the light guide of FIGS. 44 and45, in accordance with an embodiment of the present invention;

FIGS. 47-49 are simplified illustrations of light guides, in accordancewith an embodiment of the present invention;

FIG. 50 is a simplified illustration of a light intensity distributionacross the width of a wide light beam, in accordance with an embodimentof the present invention;

FIG. 51 is a simplified illustration comparing light intensitydistribution across the width of an un-reflected wide light beam withthat of a wide beam that has passed through the light guide of FIGS. 44and 45, in accordance with an embodiment of the present invention;

FIGS. 52-54 are simplified illustrations of a light guide, in accordancewith an embodiment of the present invention;

FIG. 55 is a prior art illustration of a light guide;

FIG. 56 is a simplified illustration of a light guide, in accordancewith an embodiment of the present invention;

FIGS. 57 and 58 are simplified illustrations of a light guidearrangement for detecting touches and sweep gestures performed upon thelight guide, in accordance with an embodiment of the present invention;

FIG. 59 is a simplified illustration of a touch screen having a row ofemitters along the bottom edge of the screen and a row of receiversamong the top edge of the screen, in accordance with an embodiment ofthe present invention;

FIG. 60 is a simplified illustration of the touchscreen of FIG. 59, inaccordance with an embodiment of the present invention;

FIG. 61 is an exploded view of the touchscreen of FIGS. 59 and 60, inaccordance with an embodiment of the present invention;

FIG. 62 is a simplified illustration of a touchscreen having a row ofemitters along the bottom edge of the screen mounted on a first thinstrip PCB and a row of receivers along the top edge of the screenmounted on a second thin strip PCB, in accordance with an embodiment ofthe present invention;

FIG. 63 is an exploded view of the touchscreen of FIG. 62, in accordancewith an embodiment of the present invention;

FIG. 64 is a simplified illustration of a foldable touchscreen, inaccordance with an embodiment of the present invention;

FIG. 65 is a simplified illustration of a second foldable touchscreen,in accordance with an embodiment of the present invention;

FIG. 66 is a simplified illustration of light beams from one emitterreaching all of the detectors, in accordance with an embodiment of thepresent invention;

FIG. 67 is a simplified illustration showing which beams from FIG. 66are blocked by an object touching the center of the screen, inaccordance with an embodiment of the present invention;

FIG. 68 is a simplified illustration showing additional beams from otheremitters that are not blocked by the object of FIG. 67, in accordancewith an embodiment of the present invention;

FIG. 69 is a simplified illustration showing all of the beams blocked bythe object of FIG. 67, in accordance with an embodiment of the presentinvention;

FIGS. 70-73 are illustrations of alternative LED and PD layouts for acircular touch surface, in accordance with alternative embodiments ofthe present invention;

FIG. 74 is an illustration of a light guide for a circular touchsurface, in accordance with an embodiment of the present invention;

FIG. 75 is an illustration of a PCB layout for a circular touch surface,in accordance with an embodiment of the present invention;

FIG. 76 is an illustration of light beams emitted by one LED detected bya plurality of PDs surrounding a circular touch surface, in accordancewith an embodiment of the present invention;

FIG. 77 is an illustration of a network of intersecting light beams usedin a circular touch surface, in accordance with an embodiment of thepresent invention;

FIG. 78 is a simplified illustration of a circular touch surface sensor,in accordance with an embodiment of the present invention;

FIG. 79 is an illustration of the components used to assemble a circulartouch surface, in accordance with an embodiment of the presentinvention;

FIG. 80 is an exploded view of the circular touch surface of FIG. 78, inaccordance with an embodiment of the present invention;

FIG. 81 is a cutaway view of the circular touch surface of FIG. 78, inaccordance with an embodiment of the present invention;

FIG. 82 is a simplified illustration of a light guide for the circulartouch surface of FIG. 78, in accordance with an embodiment of thepresent invention; and

FIGS. 83 and 84 are illustrations of paths of light beams used in acircular touch surface, in accordance with an embodiment of the presentinvention.

The following table catalogues the numbered elements and lists thefigures in which each numbered element appears. Similarly numberedelements represent elements of the same type, but they need not beidentical elements.

Numbered Elements Element Description Figures 101-103 emitters 1-7,32-34, 40, -42, 57, 58 104 LED chip 36, 38 105 plastic shell 36, 38106-111 emitter 21, 22, 31, 39, 44-58, 61, 63, 66-69, 83, 84 201-203,205-207 photodetector 1-7, 21, 22, 31-34, 39, 40, 50, 57, 61, 63, 66-69210 photodetector chip 43 211 plastic shell 43 220 photodetector 83300-306 light beam 1, 10, 14, 15 307, 308 blocked light beam 17, 18311-314 intersection point 10 316-319 area q 30 320-326 light beam21-26, 30, 31, 39, 40, 57, 58 327 iso-curve 24, 26 328 area q 24, 26 330iso-curve 25, 26 331 area q 25, 26 332-335 light beam 27-30, 76, 83, 84336 iso-curve 27, 29 337 area q 27, 29 338 iso-curve 28, 29 339 area q28, 29 341 light beam 44, 45 342 gap 45 343-348, 354 light beam 44-48,50 355-359 light intensity 50, 51 distribution 360 light beams 59, 66-68400 lens 36 401 entry surface 36, 38, 42, 43 402 exit surface 36, 38403-407 lens 21, 22, 31, 39, 50 410 light guide frame 40, 57 411, 412,416 light guide 41-46, 49, 51, 58 417 radius 46 419 viewing angle 46 420refractive surface 45, 46 421 reflective surface 45, 46 422 refractivesurface 45, 46 423 lens 45, 46 424 light guide 77-83 425 light shield 82429 light guide 47 430 entry surface 47 431 exit surface 47 432 air gap47 433 lens 47 440 light guide 48 441 reflective surface 48 442refractive surface 48 443 air gap 48 444 lens 48 451 curved mirror 49452 light guide 49 460 lens 52-54, 56 461 curved reflective 52, 54surface 462 curved reflective 52, 54 surface 463 entry surface 52-54 464exit surface 52-54 465 light beam 53, 54 466 upper lens portion 52, 54467 lower lens portion 52, 54 470 light guide 55 471 curved reflective55 surface 472 height of parabola 55 473 reflector 55 474 bezel height55 476 height for light 55 channel 478 height 55 479, 480 light guide59-65 481 backplane of light 55 guide 482 depth of parabola 52 483 tophorizontal plane 52, 54 484 bottom horizontal 52, 54 plane 601-605 stepin flowchart 8 612-614 screenshot 8 615-619 touch point 8, 19, 32620-624 step in flowchart 9 630 screenshot 9 633-636 light beam 9637-639 intersection point 9 640 screenshot 9 641-643 light beam 9645-647 intersection point 9 650 screenshot 9 651 circle indicating 9,11 touch area 652 PCB 41-43, 58 653-656 candidate touch 13-18 area (q)657-659 PCB 60, 61, 63 660 screenshot 9 661 pcb 75, 79-81, 83 664-671step in flowchart 35 701-705 touch point 12 710 controller 7 711calculating unit 57 715 processor 75 801-803 screen 1-5, 13-19, 21, 22,24-28, 32-34, 41-43, 49, 50, 58-68 804 crease 64, 65 810 touch plate78-81, 83 811 top cover 78-81 812 bottom cover 78-81 900 arrow 58901-904 touch point 2-5 905 touch object 21, 22, 31 906 rhomboidintersection 33 area 910 touch object 67-69 911 screw 79-81 912 wire78-80 913 haptic vibrator 79, 80

DETAILED DESCRIPTION

Aspects of the present invention relate to light-based touch screens andlight-based touch surfaces. Throughout this specification, the terms“touch screen” and “touch sensitive surface” include touch sensitiveelectronic displays and touch surfaces that do not include an electronicdisplay, inter alia, a mouse touchpad as included in many laptopcomputers and the back cover of a handheld device. They also includeairspace enclosed by the rectangular emitter-detector sensor frameprovided by the present invention.

According to embodiments of the present invention, a light-based touchsensor includes a plurality of infra-red or near infra-redlight-emitting diodes (LEDs) arranged along two adjacent edges of arectangular touch sensitive surface, as defined above, and a pluralityof photodiodes (PDs) arranged along the two remaining adjacent edges.The LEDs project light collimated in height, in order to keep itparallel to the screen surface, but the light is spread out in a widefan to reach many detectors. When this light is blocked by an insertedobject, such as a finger or a stylus, the absence of expected light isdetected by the PDs. The LEDs and PDs are controlled for selectiveactivation and de-activation by a controller. Generally, each LED and PDhas I/O connectors, and signals are transmitted to specify which LEDsand which PDs are activated. In some embodiments, each LED-PD pair isactivated separately. In other embodiments, several PDs are activatedconcurrently during an LED activation.

Reference is made to FIG. 6, which is an illustration of a network ofintersecting light beams in a touch screen system, in accordance with anembodiment of the present invention. FIG. 6 shows a first plurality ofLEDs 102, namely LED0-LED15 along the top edge of a touch screen; asecond plurality of LEDs 103, namely LED16-LED24 along the left edge ofthe touch screen; a first plurality of PDs 202, namely PD0-PD15 alongthe bottom edge of the screen; and a second plurality of PDs 203, namelyPD16-PD24 along the right edge of the touch screen. FIG. 6 alsoillustrates all of the possible emitter-detector beams.

Reference is made to FIG. 7, which is an illustration of a network ofintersecting light beams detecting five touch points in a touch screensystem, in accordance with an embodiment of the present invention. FIG.7 shows the touch screen system of FIG. 6 detecting five touches inaccordance with an embodiment of the present invention. The touches areindicated as solid black circles. The lines crossing the screen in FIG.7 indicate unblocked emitter-detector beams. A controller 710 is shownfor controlling activations of the emitters and detectors.

In some embodiments, each emitter has a respective collimating lensapart from the emitter, and each detector has a respective collimatinglens apart from the detector. In some embodiments, these collimatinglenses form a solid plastic frame along the borders of the rectangulartouch screen. In other embodiments, these collimating lenses are absentto enable a wide, 180° spread angle of light beams from each emitter.

Different emitter-detector beams have different levels of detectedintensity at their respective detectors. In an exemplary embodiment, 16diodes are arranged along the screen length and 9 diodes are arrangedalong the screen width. TABLES I and II below list the detectedintensity of unblocked beams from each emitter at each of detectorsPD0-PD15 along the screen length (TABLE I), and at each of the detectorsPD16-PD24 along the screen width (TABLE II). Empty cells indicate thatno signal is detected for the corresponding emitter-detector beam.

TABLE I Detected intensities of unblocked beams from each emitter ateach of the 15 detectors along the screen length PD0 PD1 PD2 PD3 PD4 PD5PD6 PD7 PD8 PD9 PD10 PD11 PD12 PD13 PD14 PD15 LED0 236 236 236 236 236236 236 236 180 75 39 10 LED1 236 236 236 236 236 236 236 236 236 179101 68 23 LED2 236 236 236 236 236 236 236 236 236 236 189 126 88 36 18LED3 236 236 236 236 236 236 236 236 236 236 236 174 114 47 32 7 LED4236 236 236 236 236 236 236 236 236 236 236 234 164 100 62 25 LED5 236236 236 236 236 236 236 236 236 236 236 236 217 122 75 25 LED6 236 236236 236 236 236 236 236 236 236 236 236 236 236 184 117 LED7 236 236 236236 236 236 236 236 236 236 236 236 236 236 236 162 LED8 236 236 236 236236 236 236 236 236 236 236 236 236 236 236 234 LED9 184 169 236 236 236236 236 236 236 236 236 236 236 236 236 236 LED10 139 132 165 236 236236 236 236 236 236 236 236 236 236 236 236 LED11 84 75 100 195 235 236236 236 236 236 236 236 236 236 236 236 LED12 47 49 96 205 236 236 236236 236 236 236 236 236 236 236 236 LED13 4 15 90 122 194 236 236 236236 236 236 236 236 236 236 LED14 57 75 162 197 236 236 236 236 236 236236 236 236 LED15 26 45 97 148 236 236 236 236 236 236 236 236 236 LED16236 236 44 LED17 236 236 236 61 12 LED18 145 236 236 236 183 LED19 10 50236 236 236 236 59 LED20 72 236 236 236 236 77 13 LED21 4 178 236 236235 153 120 18 LED22 1 236 216 177 160 134 70 23 LED23 57 149 180 159149 84 49 32 1 LED24 29 195 200 183 171 86 61 51 30 14 26

TABLE II Detected intensities of unblocked beams from each emitter ateach of the 9 detectors along the screen width PD16 PD17 PD18 PD19 PD20PD21 PD22 PD23 PD24 LED0 LED1 LED2 41 6 LED3 49 25 LED4 69 62 LEDS 44 4415 LED6 106 130 94 28 LED7 96 139 165 235 LED8 108 141 132 193 26 LED9125 154 169 236 153 17 LED10 123 172 201 236 236 236 LED11 27 45 117 236236 236 98 LED12 236 236 236 236 16 LED13 103 236 236 235 72 LED14 39236 236 235 LED15 49 236 235 LED16 236 171 166 170 162 164 142 142 160LED17 236 209 206 235 233 222 204 219 233 LED18 180 201 164 166 179 170147 169 192 LED19 197 224 200 209 187 165 151 199 236 LED20 191 214 193198 187 170 167 194 213 LED21 235 235 234 232 212 187 173 211 222 LED22204 215 215 226 202 192 188 209 198 LED23 197 201 217 234 209 201 173170 169 LED24 188 183 164 180 129 118 99 99 192

The maximum detection intensity in TABLES I and II is 236. A detectionintensity of at least 10 was found, by experiment, to be sufficientlygreater than a noise signal, and therefore useful for detecting touches.In some embodiments, a threshold of ½ the expected intensity is used todetermine whether a beam is blocked. Thus, if the expected intensity is236, a detection signal below 118 renders the beam as blocked, whereasif the expected intensity is 49, a detection signal below 25 renders thebeam as blocked.

In addition, certain beams were found to continue being detected evenwhen the entire screen was blocked. These beams, situated at corners ofthe touch screen, do not need to cross the screen area in order toarrive at their respective detectors. TABLE III lists the detectionvalues registered when the entire rectangular touch screen area iscovered by a solid opaque object.

TABLE III Detected intensities of blocked beams PD PD PD PD PD PD PD PDLED 0 PD1 2 PD3 4 . . . 15 PD16 17 PD18 19 PD20 21 PD22 23 PD24 0 1 2 34 5 6 7 8 9 10 11 12 13 14 235 15 44 235 235 16 236 236 40 17 236 18 13519 8 20 21 22 23 24

TABLE IV lists with an ‘x’ the useful beams in this exemplary embodimentby including beams from TABLES I and II having an unblocked detectionvalue of at least 10, and excluding the beams detected in TABLE III.

TABLE IV Usable detection beams PD PD PD PD PD PD PD PD PD PD PD PD PDPD PD PD PD PD PD PD PD PD PD PD PD 0 1 2 3 4 5 6 7 8 9 10 11 12 13 1415 16 17 18 19 20 21 22 23 24 LED0 X X X X X X X X X X X X LED1 X X X XX X X X X X X X X LED2 X X X X X X X X X X X X X X X X LED3 X X X X X XX X X X X X X X X X X LED4 X X X X X X X X X X X X X X X X X X LED5 X XX X X X X X X X X X X X X X X X X LED6 X X X X X X X X X X X X X X X X XX X X LED7 X X X X X X X X X X X X X X X X X X X X LED8 X X X X X X X XX X X X X X X X X X X X X LED9 X X X X X X X X X X X X X X X X X X X X XX LED10 X X X X X X X X X X X X X X X X X X X X X X LED11 X X X X X X XX X X X X X X X X X X X X X X X LED12 X X X X X X X X X X X X X X X X XX X X X LED13 X X X X X X X X X X X X X X X X X X X LED14 X X X X X X XX X X X X X X X X LED15 X X X X X X X X X X X X X LED16 X X X X X X X XX LED17 X X X X X X X X X X X X X LED18 X X X X X X X X X X X X X LED19X X X X X X X X X X X X X X X LED20 X X X X X X X X X X X X X X X XLED21 X X X X X X X X X X X X X X X X LED22 X X X X X X X X X X X X X XX X LED23 X X X X X X X X X X X X X X X X X LED24 X X X X X X X X X X XX X X X X X X X X

Touch Coordinate Method

This section describes in detail the operations to determine a trackedobject's location. Reference is made FIG. 8, which is a flow chartdescribing a first method for identifying touch locations, in accordancewith an embodiment of the present invention. FIG. 8 shows a first methodfor calculating touch positions. At step 601 the touch sensitive area isparsed into a two-dimensional (2D) pixel or cell grid. In addition, atable is generated storing a list of pixels or cells traversed by eachactive detection beam marked in TABLE IV. In some embodiments, the tableis stored as a list of pixel entries, each pixel entry storing a list ofbeams that pass through the pixel. In other embodiments, the table isstored as a list of light beam entries, each light beam entry storing alist of pixels along its beam path. Step 601 is performed offline. Insome embodiments, the cells are of different sizes depending onlocation. For example, at the center of the screen the cells are smallercorresponding to the high density of beams vis-à-vis cells near theedges of the screen where the density of beams is lower. In someembodiments, the cells are not aligned along a two dimensional grid.Rather, each cell surrounds a point of intersection between two beams.

At step 602 a scan is performed for all usable beams listed in TABLE IV.Each beam is marked as either blocked or unblocked, according to adetection threshold, as described hereinabove. Screenshot 612illustrates the unblocked beams in a case of five simultaneous touches.

At step 603 each pixel in the 2D cell grid from step 601 receives abinary value (blocked=1/not blocked=0). This binary value is a logicalAND between all of the binary values from step 602 of LED-to-PD lightbeams that pass through the cell, according to the stored list from step601. Thus, in this method unblocked beams are used to mark cells asuntouched. A single, unblocked beam passing through a grid cell issufficient to mark the cell as untouched. According to an alternativemethod described below intersections of blocked beams are used to fillthe grid from step 601. Screenshot 613 illustrates cells marked asuntouched (white) and touched (black).

At step 604 touch areas are formed by connecting neighboring blockedgrid cells: for each pixel in step 603 having a value of 1 (blocked),four immediate neighbors are checked, namely, top, bottom, left andright neighbors. Any neighbor having a value of 1 is connected.Screenshot 614 illustrates five touch locations 701-705 identified byjoining connected neighbors.

At step 605 the touch coordinates and area of each touch location arecalculated. In some embodiments, the area of a touch location is the sumof its pixels and the touch position is the center of gravity of thearea. In some embodiments, a valid touch location must have a minimumarea, e.g., based on the expected size of a finger. Furthermore, in someembodiments a maximum size for a touch object is also provided. When atouch area exceeds the maximum size it is either discarded or it isassumed to contain multiple objects placed together on the screen. Thus,the touch sensor is operable to distinguish between a single fingerperforming a gesture and multiple fingers placed together performing thesame gesture. Similarly, when the system tracks multiple touch objects,the system is operable to continue tracking them as multiple objectseven after they are brought together based on the large size of thetouch object, e.g., in a pinch gesture.

Reference is made to FIG. 9, which is a flow chart describing a secondmethod for identifying touch locations, in accordance with an embodimentof the present invention. At step 620 a lookup table of intersectionpoints between light beams is generated. In this table, every entryincludes, for each light beam of the usable light beams listed in TableIV, other beams that intersect that beam and their respective points ofintersection, and for each point of intersection the lookup tableincludes pointers to four neighboring intersection points, namely twoimmediate neighboring intersection points along each of the twointersecting beams. These neighboring intersection points areillustrated in FIG. 10.

Reference is made to FIG. 10, which is an illustration of neighboringintersections used by the method of FIG. 9, in accordance with anembodiment of the present invention. FIG. 10 shows two primaryintersecting beams 301, 302 intersecting at point 310. Two additionalbeams, 303, 304, also intersect beams 301, 302 at points 311-314. Thelookup table entry for intersection point 310 includes the coordinatesof point 310 and pointers to neighboring intersection points 311-314.

Returning to FIG. 9, at step 621 all usable beams, as listed in TABLEIV, are scanned and assigned a binary blocked/unblocked value bycomparing the beam's detection value to a threshold. In someembodiments, a normalized detection value is used instead of a binaryvalue; the normalized values from neighboring beams are theninterpolated to refine the touch location calculation.

At step 622 blocked beams are analyzed in the following manner. When afirst blocked beam is identified, the method checks every intersectionpoint along the blocked beam to see if that point is an intersection oftwo blocked beams. When such an intersection point is identified, themethod recursively checks all immediate neighboring intersection pointsfor additional intersections of two blocked beams until no furtherintersection points of two blocked beams are found. All neighboringintersection points that are also formed by two blocked beams areassumed to belong to the same touch object and are therefore groupedtogether. This recursive method finds all of the connected intersectionsbelonging to a single touch object. The method is then repeatedbeginning with a blocked beam not already used in the previous steps.The resulting network of connected intersection points, where pairs ofblocked beams intersect, is illustrated inside circle 651 in FIG. 11.

Reference is made to FIG. 11, which is an illustration of a network ofconnected blocked beams used to locate a touch object, in accordancewith an embodiment of the present invention. FIG. 11 shows blocked andnon-blocked beams in a case of one touch. FIG. 11 is a color figure.Green lines represent non-blocked beams and red lines represent blockedbeams. Thus, a significant intersection point is a point at which twored lines intersect. From a first such red intersection point, thecurrent method recursively builds a network of connected redintersections. This area is the red area marked in FIG. 11 by yellowcircle 651.

Step 622 is illustrated by frame 640 in FIG. 9. Frame 640 includes afirst blocked beam 633. Three intersection points 637-639 along beam 633are shown. Points 637 and 638 are where beam 633 intersects twonon-blocked beams, 634 and 635, respectively. Point 639 is anintersection between beam 633 and a second blocked beam 636.Intersecting beam 636 is the second blocked beam identified by thismethod.

At step 623 the method recursively checks intersection pointsneighboring point 639 to create a network or web of neighboringintersections that belong to the same touch object. This is illustratedin FIG. 9 by frame 650, showing first intersection point 639 andneighboring intersection points 645-647. Point 647 is the nextintersection point along beam 633; points 645 and 646 are neighboringintersections along second blocked beam 636. Point 645 is where beam 636meets beam 643, and point 646 is where beam 636 meets beam 641. Therecursive nature of this step means that if any of these points 645-647are also formed by two blocked beams, the search expands to theirneighbors. The list of neighboring intersections is generated offlineand stored in memory. The method begins by sequentially checking thebeams. The first blocked beam branches the search to check itsneighbors. A list of checked beams is used to avoid checking neighborbeams again when the method resumes sequentially checking for a firstblocked beam.

At step 624 the method proceeds to analyze the connected intersectionpoints to extract the first and last blocked intersection point on eachbeam. This provides an outline of the touch area. Thus, in FIG. 11,these outermost points form yellow circle 651 that surrounds thenetwork, or web, of red lines. A miniaturized version of FIG. 11 ispresented in frame 660 in FIG. 9, with yellow circle 651 surrounding theweb of red beams. The touch location is calculated as the average ofthese two endpoints for all beams. The width and height of the toucharea are calculated by determining the area's left, right, top andbottom coordinates. These are determined by the maximum and minimumcoordinates of intersection points in each direction, or alternatively,by averaging the coordinates of two or three maximum and minimumintersection points in each direction.

If a candidate touch location includes at least one unique blocked beam,i.e., if a blocked beam that does not pass through any other candidatetouch locations, then it is confirmed to be an actual touch location. Ifno unique blocked beam corresponds to a candidate touch location, i.e.,if all blocked beams passing through the candidate location pass throughat least one other confirmed touch location, then that candidate touchlocation is discarded. In this way phantom touches, i.e., locationscorresponding to intersections of blocked beams that are not generatedby an object at the intersection location, but rather by two objectsthat cast a light-beam shadow on that location, are discarded.

Reference is made to FIG. 12, which is a map of locations at whichdetection beams intersect. As explained hereinabove, intersections forwhich every intersecting beam is blocked is marked as a blockedintersection. Blocked intersections are shaded black in FIG. 12. FIG. 12shows five clusters of blocked intersections 701-705 corresponding tofive touch objects identified by the system and methods describedhereinabove. Additional blocked intersections are shown, but they belongto clusters too small to quality as touch objects.

Reference is made to FIGS. 13-18, which are illustrations of analternative method for determining touch locations, whereby portions ofa large, candidate touch area are excluded based on unblocked thin lightbeams, in accordance with an embodiment of the present invention. Themethod uses very thin beams and assumes that any object touching thescreen has a radius of at least d. The method begins by defining theentire screen as a potential touch area Q in which touch objects ofradius d may be present. FIG. 13 shows a screen 802 with area Qindicated by shaded area 653. An unobstructed narrow beam indicates thatno object having radius d is located within a distance d from the beam.This situation is illustrated in FIG. 14 showing unobstructed, narrowbeam 305 passing across screen 802. Based on the assumption that anytouch object has a radius d, it is evident that no such touch object islocated within distance d of beam 305. Therefore a corridor having awidth of 2d along beam 305 is removed or excluded from Q, splitting Qinto two polygons 653 and 654. As more unobstructed beams are added,more areas are removed from Q. Thus, in FIG. 15 two unobstructed beams305 and 306 are shown, whereby Q is divided into four polygons 653-656.Eventually, Q becomes an increasing number of separate, convex polygons,with an increasing number of edges, as illustrated in FIG. 16, where Qhas been reduced to three convex polygons 653-655. When implementingthis method it is sometimes advantageous to advance through neighboringbeams rather than distant beams. For example, referring back to FIG. 15,it can be seen that a second unblocked beam alongside beam 305 wouldreduce the size of Q without adding any additional polygons, whereas inFIG. 16 unblocked beam 306 adds two new polygons 355 and 356. Additionalpolygons in Q require, inter alia, more memory to store the additionalpolygon data.

In some implementations, the method does not proceed beyond dividing Qbased on unblocked narrow beams. The method ends when all unblockedbeams have been analyzed. Each remaining polygon in Q is assumed tocontain a touch object, but the object's location within the polygon isunknown. Reference is made to FIG. 16 showing three polygons 653-655remaining in Q, and thus three objects are assumed to be touching screen802 at these three locations, respectively. In some embodiments eachpolygon's center of gravity is assumed to be center of its respectivetouch object.

Certain touch patterns will generate more separate polygons in Q thantouch points. These extra polygons are known as ghost points. One way ofdisambiguating or eliminating ghost points is to continue the methodwith a second step of analyzing blocked beams, as explained withreference to FIGS. 17 and 18. Each blocked beam i indicates a regionO_(i) along the beam containing at least one touch object with radius d.Since touch objects can only exist in Q, there is at least one objectwhere O_(i) intersects Q, i.e., O_(i)∩Q≠Ø. FIG. 17 shows blocked beam307. Two polygons in Q lie within a distance d from the path of thisbeam, namely, polygons 654 and 655, and both polygons are equally likelyto contain the blocking object. In order to resolve this ambiguity, onlypolygons in Q having a unique blocked beam, i.e., the blocked beampasses through only one polygon in Q, are assumed to contain a touchobject. FIG. 18 shows a second blocked beam 308. Only one polygon in Qlies within a distance d from the path of this beam, namely, polygon655. Therefore, polygon 655 definitely contains a touch object. Polygon654 may contain an additional touch object, or it may be a ghost point.In cases when multiple objects are being tracked, polygons in Q crossedby non-unique blocked beams that seem to correspond to a tracked objectare assumed to contain the tracked object. Thus, if the location of 654corresponds to a previously tracked touch object, polygon 654 isassigned a touch object, but otherwise it is ignored as a ghost point.

The center of an assumed touch object is the center of gravity of itspolygon Q. Alternatively, the center of an assumed touch object is thecenter of gravity of the polygon defined by O_(i)∩Q, which may besmaller than polygon 654. Thus, polygons in Q traversed by a uniqueblocked beam definitely contain a touch object, whereas polygons in Qnot traversed by a unique blocked beam but only by blocked beams thattraverse multiple polygons in Q possibly contain a touch object. In someembodiments, these possible touch candidates are reported as possible,not definite, touch locations.

Reference is made to FIG. 19, which is an illustration of five circles615-619 indicating areas though which no beams pass due to touchobjects, in accordance with an embodiment of the present invention.Using the method illustrated in FIGS. 13-18, area Q inside each circleis the resulting touch candidate area. Thus, five touch objects areidentified using only the unblocked beams shown in FIG. 19.

Reference is made to FIG. 20, which is a graph tracking the number ofseparate touch candidate areas as a function of the number of unblockedbeams, in accordance with an embodiment of the present invention. Thex-axis represents the number of beams analyzed in a touch system, andthe y-axis represents the number of individual polygons identified in Q.After analyzing 150 beams, six separate polygons are identified in Q.However, once 250 beams have been analyzed, one of the polygons waseliminated because some of the unobstructed beams 150-250 passed withind of the sixth polygon, removing it from Q.

In order to detect a touch object, having an assumed minimum diameter d,anywhere on the screen, every location on the screen must be within adistance d of at least one beam. Therefore, any area not within adistance d of at least one beam is identified and removed from Q. Putanother way, any area farther than d from all beams is an undetectablearea R. Any area common to Q and R, namely, R∩Q, is a blind area. Suchareas are defined by the beam layout and by the size of d and should bemasked out of Q as it is not possible to determine if an object will bepresent there.

A variation of the method that excludes portions of area Q based onunblocked beams is now described. The method described above uses narrowbeams, such that a beam is either blocked or unblocked, i.e., each beamhas a binary state. The variation uses wide beams that can be partiallyblocked. In the case of wide beams an amount of blockage is used todetermine where within the beam the blocking object may be located andexcluding the remaining portion of the beam from Q.

Reference is made to FIGS. 21 and 22, which are simplified illustrationsof a partially blocked wide beam, that illustrate effects of where ablocking object is placed, in accordance with an embodiment of thepresent invention. FIG. 21 shows beams of light 323 and 324 exiting froman extended emitter lens 404 and arriving at an extended receiver lens403. A wide beam from emitter 106 passing through lens 404 to receiver206 via lens 403 can be simulated as a series of point-source beamsoriginating along lens 404, each point-source beam spreading to coverreceiver lens 403. Two such beams are shown in FIG. 21, namely beams 323and 324. In FIG. 21, touch object 905 blocks a portion of these beamsfrom reaching the left edge of receiver lens 403. The method assumesthat any blocking object, e.g., pointer 905, has a radius of at least dand that the object blocks the beam from one of the beam's edges inward.Thus, the amount of expected light that is absent at receiver 206indicates the extent that a touch object of radius d has entered thisbeam. FIG. 21 illustrates beam blockage when object 905 is insertedmid-way between lenses 404 and 403. Greater amounts of light are blockedwhen object 905 is inserted nearer to either lens 404 or lens 403 andobject 905 is inserted less than half-way through the beam.

FIG. 22 shows object 905 inserted near emitter lens 404, and its effecton simulated point-source beams 323 and 324. In this case the totalamount of detected light at receiver 206 is less than the amountdetected in the case of FIG. 21, even though object 905 is inserted tothe same extent through the wide beam (from lens 404 to lens 403). Asimilar amount of light is detected when object 905 is inserted nearlens 403.

Thus, when an object having a radius d blocks a portion of a wide beam,the portion extending from the side of the beam inward, the outer edgeof the object must be somewhere along a curve within the beam. Beamlight intensities for all possible touch points of an object with radiusd are calculated numerically using the model illustrated by FIGS. 21 and22.

Reference is made to FIG. 23, which is a simplified exemplaryillustration of iso-curves across the width of a wide light beam, inaccordance with an embodiment of the present invention. FIG. 23 showsthe result of the above calculation displayed as a set of solid curves.The dashed curves are an approximation using a least squares fitpolynomial. The solid and dashed curves are referred to as “iso-curves”(iso means equal). Thus, if the outer edge of the touch object isanywhere along an iso-curve the amount of light detected is the same.

In some embodiments of the present invention, the iso-curves aremeasured on the device. This is particularly suitable for systems thatemploy complex light guides in which the light intensity distributionacross the width of the wide beam is not a simple curve, such as thelight guide illustrated in FIG. 44, as explained below with reference toFIG. 51. In other embodiments of the present invention, the iso-curvesare calculated as follows. When the beam is obstructed from the left tosome edge (x, y), light emitted from position a on the source will shineon the sensor from the projection of the edge β₀, to the right edge ofthe sensor. Integrating the lit up ratio of the sensor over all emittingpositions gives the total detected light intensity from the sensor. Leftto right for x, α and β₀ range from 0 to 1, and y—the coordinate alongthe beam from source to sensor, also ranges from 0 to 1. The formulasfor calculating the intensity ratio I are given by Equations (1) and(2):

$\begin{matrix}{{\beta_{0}\left( {x,y,\alpha} \right)} = \left\{ {\begin{matrix}{1,} & {\gamma > 0} \\{0,} & {\gamma < 0} \\{\gamma,} & {otherwise}\end{matrix},{\gamma = {\alpha - \frac{x - \alpha}{y}}}} \right.} & (1) \\{I = {{\int_{\alpha = 0}^{1}1} - {{\beta_{0}\left( {x,y,\alpha} \right)}{\alpha}}}} & (2)\end{matrix}$

In some embodiments of the present invention, the iso-curves aremeasured on the device and added as a multiplier along with α and β₀.

FIG. 23 illustrates a plurality of iso-curves in wide beam 325representing steps of 5% of the unobstructed light intensity. Thus, theleftmost curve represents the possible locations of the object's outeredge when 5% of the intensity of beam 325 is blocked, the second fromleft represents 10% blocked intensity, etc. The iso-curves marking thepossible object edge on the right half of beam 325 are a mirrorreflection of the iso-beams on the left half of beam 325. Although FIG.23 illustrates specific iso-curves, they are not quantum steps, asevidenced by Equations (1) and (2) above. Rather, the iso-curvesprogress linearly across the entire width of beam 325 and theillustrated curves in FIG. 23 are merely examples.

Conceptually, each iso-curve is the equivalent of a thin beam in theprevious method. That is, in the previous method, an unblocked thin beammeans that the object of radius d was at least a distance d away fromthe beam path. Similarly, when for example 20% of wide beam 325 isblocked, that means that, with reference to the iso-curves in FIG. 23,the edge is somewhere along the fourth iso-curve from the left, or thefourth iso-curve from the right. The object cannot be right of thefourth-from-left iso-curve or to the left of the fourth-from-rightiso-curve and thus these areas are removed from Q. Moreover, because themethod is searching for the center coordinates of the touch object, amargin of width d along these iso-curves can further be removed from Q.This process is explained with reference to FIGS. 24-30.

Reference is made to FIGS. 24-30, which are simplified illustrations ofa method of touch location determination, whereby portions of a large,candidate touch area are excluded based on unblocked, and partiallyblocked, wide light beams, in accordance with an embodiment of thepresent invention. FIG. 24 shows the center 326 of a partially blockedwide beam crossing the screen. The amount of expected light missing fromthis wide beam is less than 50%; i.e., more than 50% of the beam's lightwas detected. A corresponding iso-curve 327 is shown to the left ofcenter 326 indicating a border along which the object blocking this beammay be located. The object may be located anywhere to the right ofiso-curve 327, but it cannot extend to the left beyond this iso-curve.Thus the area covered by this wide beam and left of iso-curve 327 can beremoved from Q, assuming the object entered the beam from the beam'sright edge. Moreover, because the method seeks the coordinates of thecenter of the object, a margin of width d to the right of iso-curve 327can be further removed from Q. The area remaining in Q is area 328.

FIG. 25 shows center 326 of the same beam as in FIG. 24, but shows how Qis reduced when the object was inserted into this wide beam from theleft. The corresponding iso-curve 330 is shown, to the right of which,the object cannot be located. And an additional margin having width d isshown along iso-curve 330 inside which the center of the object cannotbe located. The area thus remaining in Q is shaded area 331.

FIG. 26 shows the areas 328 and 331 remaining in Q (in screen 802) basedon this partially detected wide beam. Thus, areas 331 and 328 areconvex, as a result of the fact that more than 50% of the wide beam wasdetected, in other words, less than 50% of the beam was blocked. Whenless than 50% of the wide beam is detected, the resulting areas in Q areconcave, as explained below.

FIG. 27 shows the center 335 of a wide horizontal beam that is partiallyblocked. In this case, more than 50% of the beam is blocked, i.e., lessthan 50% of the expected light for this beam was detected. As above, itis unknown from which side of the beam the object entered the beam. FIG.27 shows shaded area 337 as the remaining area Q if the object wasinserted into the beam from below. In this case, iso-curve 336 is thecurve along which the outer edge of the object may lie. It is noted thatbecause the object is assumed to have been inserted from the bottom ofthe beam, and blocks more than 50% of the wide beam's light, the objectis assumed to cover center 335 of this beam and iso-curve 336 istherefore above center 335. The object cannot extend upward of iso-curve336 and therefore this area within the wide beam is removed from Q.Also, because this method searches for the center of the object, amargin of width d, the assumed radius of the object, below iso-curve 336can also be removed from Q. Thus, the area remaining in Q is shaded area337.

FIG. 28 shows how much remains in Q when it is assumed that the objectenters the beam from above. FIG. 28 shows the center 335 of the beam,iso-curve 338 below center 335, and shaded area 339 remaining in Q. Theborder of area 339 is offset a margin d from iso-curve 338.

FIG. 29 shows the area remaining in Q after analyzing this horizontalbeam that is mostly blocked, by combining the results of FIGS. 27 and28. Areas 337 and 339 remaining in Q are concave.

FIG. 30 shows a map of remaining areas Q after combining the analyses ofthe beams in FIGS. 26 and 29. Q is now made up of four separate areas316-319.

Although the illustrated wide beams span an area between opposite sidesof screen 802, this method also applies to beams that span an areabetween adjacent screen edges. Reference is made to FIG. 31, which is asimplified illustration of a partially blocked wide beam that extendsbetween two adjacent screen edges, in accordance with an embodiment ofthe present invention. FIG. 31 shows a diagonal beam extending from abottom edge to the right edge of the screen. The wide beam generated byLED 106 and emitter lens 404 terminates at receiver lens 403 whichdirects the beam to receiver 206. An object 905 is blocking a portion ofthe beam. Two simulated point-source beams 323 and 324 are shown,similar to those in FIGS. 21 and 22. Based on the calculations describedhereinabove, a set of iso-curves is calculated for this beam to mappossible edges of an object according to the amount of the beam that isblocked.

Reference is made to FIGS. 32-34, which are simplified drawings of anobject being detected, in accordance with another method of the presentinvention, utilizing wide light beams. In some embodiments of thepresent invention, opposing rows of emitters and receivers are used,each emitter being opposite a respective receiver, whereas in otherembodiments of the present invention the emitters are shift-aligned withthe receivers. For example, each emitter may be positioned opposite amidpoint between two opposing receivers, or each emitter may be off-axisaligned with an opposite receiver, but not opposite the midpoint betweentwo receivers. In addition, certain embodiments employ collimatinglenses coupled with a surface of micro-lenses that refract light to formmultiple wide divergent beams. A discussion of these differentembodiments is included in co-pending U.S. Pat. No. 8,674,966 entitledASIC CONTROLLER FOR LIGHT-BASED TOUCH SCREEN, incorporated by referencehereinabove. Once touch locations have been determined using any of thesystems and methods described in U.S. Pat. No. 8,674,966, the presentapplication teaches how to resolve possible ghost touches.

FIG. 32 shows touch location 616, the initial location of which on thehorizontal axis of screen 802 is determined based on a weighted sum oftwo detection signals: the partially blocked beams from emitter 101 toreceiver 201, and from emitter 101 to receiver 202. That is, the beamsfrom emitter 101 to receiver 201 and from emitter 101 to receiver 202are wide beams and each beam has a respective coordinate value along thehorizontal axis of screen 802, X_(a) and X_(b). The coordinate valueassociated with each beam is assigned a weight W, corresponding to theamount of light blocked from that beam by the object at location 616.The location is thus determined using the weighted average

X _(P)=(W _(a) X _(a) +W _(b) X _(b))/(W _(a) +W _(b)),  (3)

where the weights W_(a) and W_(b) are normalized signal differences forthe two beams.

If the pointer is detected by more than two emitter-receiver pairs, thenthe above weighted average is generalized to

X _(P)=Σ(W _(n) X _(n))/(ΣW _(n)),  (4)

where the weights W_(n) are normalized signal differences, and the X_(n)are weight positions. These calculations are described in U.S. Pat. No.8,674,966, with reference to FIGS. 137 and 143-150 therein, based on aninitial assumed Y axis coordinate of the touch. Thus, both anX-coordinate and a Y-coordinate are determined initially. For the sakeof exposition, the beams crossing screen 802 in a vertical direction,e.g., beams 101-201 and 101-202, are referred to as vertical wide beams,and beams crossing screen 802 in a horizontal direction, e.g., beamsbetween emitters and receivers along the left and right sides of screen802, are referred to as horizontal wide beams.

In order to refine the touch coordinate further and resolve anypossibility that this determined location is actually a ghost point, asecond set of calculations is performed. The first step in this secondprocess is to assemble a list of all of the vertical wide beams thatcontributed to the X coordinate calculation, e.g., beams 101-201 and101-202 in the example of FIG. 32. For each vertical wide beam in thislist, a secondary list is compiled of all wide beams from any emitter onthe right side of the screen to any receiver on the left of the screenthat crosses the determined location. FIG. 33 shows two intersectingwide beams: vertical wide beam 101-201 and horizontal wide beam 102-203.The secondary list of wide beams crossing beam 101-201 and also coveringcoordinate 616 is illustrated in FIG. 34. A similar secondary list iscompiled for wide beams crossing beam 101-202 and also coveringcoordinate 616.

Thus, numerous pairs of intersecting beams are identified in which theintersection covers the determined location. Each such intersectionbetween two wide beams forms a two-dimensional shape, such as rhombus906 in FIG. 33. The center of gravity of each rhombus is used as acoordinate in calculating a weighted sum to refine the touch location.However, if any of the intersecting beams in the secondary list isentirely unblocked, it is evident that the current touch location is aghost touch, not a real touch.

When all of the intersecting beams in the secondary list are at leastpartially blocked, the touch location is refined by calculating aweighted sum using the center of gravity of each rhomboid intersectionarea multiplied by a weight corresponding to the degree to which thatrhomboid's intersecting horizontal beam is blocked. In some embodiments,the weight corresponds to the degree to which both of that rhomboid'sintersecting beams are blocked—i.e., both the vertical beam and thehorizontal beam.

This process is repeated for the Y coordinate calculation, usinghorizontal beams that contribute to the initial Y coordinatecalculation. In this case, the secondary list for each horizontal widebeam includes wide beams from any emitter along the top edge of thescreen to any receiver along the bottom edge of the screen that coversthe initial touch location.

Reference is made to FIG. 35, which is a flowchart for a method ofeliminating ghost touches, in accordance with an embodiment of thepresent invention. At step 664, an initial set of possible touchcoordinates is calculated using only vertical and horizontal lightbeams, but not diagonal beams. In systems in which the emitters areshift-aligned with the receivers, only shift-aligned emitter-receiverpairs are used. This includes divergent pairs of beams from one emitterto two receivers.

Step 665 is a loop that iterates over each touch candidate calculated instep 664. Step 666 is a loop over the x and y coordinates of each touchcandidate. The body of this inner loop is steps 667-671.

At step 667 the system compiles a list of all beams that cross one ofthe beams used in step 664 and also traverse the coordinate calculatedin step 664. In some embodiments this is done by consulting a look uptable. In other embodiments, calculations are used to compile this list.

At step 668 the system checks whether any of these incident beams iscompletely unblocked. If any of these beams is completely unblocked, thecandidate touch location is determined to be a ghost point (step 669)and the system advances to the next touch candidate.

If all of the beams at step 668 are partially blocked, the systemrefines the touch coordinate by calculating a weighted sum of all of theincident beams crossing this touch location. The rhomboid area ofoverlap between each of the wide beams used in step 664 and each of thewide beams identified in step 667 is calculated at step 670. Then thecenter of gravity of this area is calculated, and the center ofgravity's coordinate along the desired axis is used in the weighted sum.A respective weight is assigned to each center of gravity according tothe degree to which the incidental beam is blocked. The refined touchcoordinate is a weighted sum of all the center-of-gravity coordinatesalong the desired axis, calculated at step 670. This weighted sum iscalculated at step 671.

Lenses

In some embodiments of the invention each LED and each PD is coupledwith a lens. This section explains several lens structure alternativesthat maximize the amount of light utilized for touch detection.

A first lens is acylindrical, with a progressive focal length, in orderto keep good focus on the associated LED or PD chip for all angles.Reference is made to FIG. 36, which is a simplified drawing of a lensthat distributes beams across many angles, in accordance with anembodiment of the present invention. FIG. 36 is a view from above,showing an LED chip 104 emitting light beams through its plastic shell105 and into lens 400 of the present invention. Lens 400 has a curvedentry surface 401 and a flat exit surface 402. Four beams are shownexiting the lens at angles of 0°-60°. However, a continuous array ofbeams exits along the lens exit surface 402, and their angles graduallyincrease along the exit surface 402. The curvature of entry surface 401is optimized for this progression of exit angles. Entry surface 401 isonly curved in the plane perpendicular to the screen, and thus has nooptical power in the plane of the screen.

Reference is made to FIG. 37, which is a simplified figure of fourdifferent fields of view that are all focused on a single diode, inaccordance with an embodiment of the present invention. FIG. 37 iscomposed of four side views of fields of collimated beams each enteringthe light guide at a different angle, namely the same angles shown inthe FIG. 36 view from above. Despite these different angles, FIG. 37shows how all four fields are focused on the diode chip, despite theirlargely varying effective focal lengths.

Reference is made to FIG. 38, which is an illustration of the fourfields of view of FIG. 37 as viewed from above, in accordance with anembodiment of the present invention. FIG. 38 shows a short focal lengthf0 for 0° and a long focal length f60 for 60°. The same numberedelements represent the same objects, in FIGS. 36 and 38. Although lens400 is described with reference to LED 104, identical lenses are usedfor the PDs as well.

Reference is made to FIGS. 39 and 40, which are illustrations of twobeams from one emitter to two respective PDs, in accordance with anembodiment of the present invention. FIG. 39 shows how beams from oneLED 106 arrive at two PDs 205 and 206 as a result of lenses 405-407.Shown in FIG. 39 are beam 320 from LED 106 to PD 205 and beam 321 fromLED 106 to PD 206. FIG. 40 shows beams 320 and 321 inside an entirelight guide frame 410 surrounded by LEDs 102-103 and PDs 202-203.

Reference is made to FIGS. 41-43, which are illustrations of anarrangement of components, light guides, PCB and screen in a device, inaccordance with an embodiment of the present invention. FIG. 41 shows aportion of a touch screen assembly according to the present invention.Two light guides 411 and 412 are placed along two perpendicular edges ofscreen 802. An array of LEDs 103 is arranged on PCB 652 behind lightguide 411.

FIG. 42 shows a view from above of a portion of the arrangement shown inFIG. 41. FIG. 42 shows one LED 103 facing light guide 411; PCB 652 andscreen 802. Curved inner lens surface 401 faces LED 103.

FIG. 43 shows a side cutaway view of a portion of the arrangement shownin FIG. 41, except that LED 103 is replaced by PD 210 encased in PDshell 211. FIG. 43 also shows light guide 411 having inner surface 401,PCB 652 and screen 802. In the cross-section view shown in FIG. 43 innersurface 401 is curved along its height in order to collimate light alongthe height of lens 411, i.e., perpendicular to the screen. Thiscross-section is through the optical axis, which is the center of PD201, and the curve seen is for the forward 0° field illustrated in FIGS.36-38. If the cross-section were done in another plane, the curvaturewould be different to suit the corresponding field angle.

A second option is a light guide featuring both refractive elements andreflective elements. This light guide enables utilizing light emittedfrom the LED at more extreme angles than lenses that use onlyrefraction, thereby gathering more of the emitted LED light. This lightguide allows for a wider pitch within a limited space in the lightdirection, i.e., a more extreme ratio between the pitch and thedepth/length from the chip to the end of the light guide.

Reference is made to FIGS. 44 and 45, which are simplified illustrationsof a light guide, in accordance with an embodiment of the presentinvention. FIG. 44 shows a light guide 416, three light emitters 107-109and the “pitch” and “depth” mentioned above. FIG. 45 shows a compoundlens embodiment, including light guide 416 and three LEDs 107-109. Lightguide 416 has three identical sections, one opposite each of the LEDs.Similar compound lenses are used for the PDs. Light guide 416 has anexceptionally wide viewing angle 419 as a result of refractive surfaces420 and reflective surfaces 421. Light directed forward from the emitteris not reflected; it is collimated by collimating optical surface 422.

Thus three portions of the output light field 343 are: central,collimated portion 344, and left and right collimated portions 345 and341. Two gaps 342 in output light field 343 are shown. These are causedby radii 417 joining refractive surface 420 to refractive surface 422and to reflective surface 421, respectively. Several methods areprovided for covering gaps 342, using either microstructures, air gapsin the light guide, or a combination thereof. The air gap solutionsclose gaps 342, whereas the microstructure configurations reduce theseverity of gaps 342, but do not remove them entirely.

Reference is made to FIG. 46, which is a simplified illustration of howmicrostructures reduce the problem of gaps in the light field, in thelight guide of FIGS. 44 and 45, in accordance with an embodiment of thepresent invention. FIG. 46 shows the effect of light-scatteringmicro-structures applied to outer lens surface 423. Gaps 342 in lightfield 341 illustrated in FIG. 45 are now covered by scattered beams 346.

Another method of covering gaps 342 uses an air-gap in the light guide.Two variations are provided. Reference is made to FIGS. 47-49, which aresimplified illustrations of light guides, in accordance with anembodiment of the present invention. FIG. 47 shows light guide 429separated by air gap 432 from lens 433. Lens 433 may be a flattransparent sheet used to provide a straight border to the touch area.Light guide 429 differs from light guide 416 mainly in its centralcollimating portion. In light guide 416 the forward-directed light iscollimated by a single refraction at entry surface 422, whereas in lightguide 429, this light is collimated by two refractions: at entry surface430 and at exit surface 431. The refraction at entry surface 430 directsthe light such that when it exits surface 431, it covers the gap in thelight field, as illustrated by light field 347.

FIG. 48 shows an alternative light guide 440 that covers gaps 432 bydirecting light in the left and right portions of light guide 440,instead of the in the central portion. Light guide 440 is separated byair gap 443 from lens 444. Lens 444 may be a flat transparent sheet usedto provide a straight border to the touch area, as lens 433 in FIG. 47.Light guide 440 differs from light guide 416 mainly in its left andright reflecting and refracting portions. In light guide 416 thewide-angle light is collimated by a refraction at entry surface 420followed by a reflection at surface 421, whereas in light guide 440, onefurther refraction is required at exit surface 442. The reflection atsurface 441 directs the light such that when it exits surface 432, itcovers the gap in the light field, as illustrated by light field 348.

Light guides 416, 429 and 440 all collimate light in a first dimension,parallel to the screen surface. A curved mirror is used to collimate thelight beams in the dimension incident to the screen surface. FIG. 49shows LEDs 107-109, light guide 416 for collimating light from theseLEDs in a first direction, and curved mirror 451 for collimating theselight beams in a second direction. A second light guide 452 directsthese beams across screen 802.

For some methods it is useful that the beam intensity varies linearlyalong the width of light field 343. Reference is made to FIG. 50, whichis a simplified illustration of a light intensity distribution acrossthe width of a wide light beam, in accordance with an embodiment of thepresent invention. FIG. 50 shows linear light intensity distribution 355across the width of wide beam 354. The other elements in FIG. 50 arescreen 802, LED 106 and its associated lens 407, PDs 205 and 206, andtheir associated lenses 405, 406. Reference is made to U.S. PublicationNo. 2011/0163998 A1 entitled OPTICAL TOUCH SCREEN SYSTEMS USINGREFLECTED LIGHT, the contents of which are incorporated herein in theirentirety by reference, which explains how a linear light intensitydistribution is used to determine a touch location inside a wide beam.However, due to the reflection at the outer edges of light guides 416,429 and 440, the outer sections of light field 343 are inverted, as willbe explained with reference to FIG. 51.

Reference is made to FIG. 51, which is a simplified illustrationcomparing light intensity distribution across the width of anun-reflected wide light beam with that of a wide beam that has passedthrough the light guide of FIGS. 44 and 45, in accordance with anembodiment of the present invention. FIG. 51 compares the lightintensity distributions from a first emitter 106 with those from asecond emitter 108 passing through light guide 416. The lineardistribution 356 from emitter 106 is rearranged by light guide 416 intothree distributions 357-359. Distributions 358 and 359 are directionallydifferent than their neighboring portions of distribution 357. Themicrostructures discussed in reference to FIG. 46 ameliorate thisproblem. However, an alternative light guide avoids this problementirely while still capturing a wide viewing angle.

Reference is made to FIGS. 52-54, which are simplified illustrations ofa light guide, in accordance with an embodiment of the presentinvention. FIG. 52 shows three lenses 460 of a light guide that alsocaptures a wide viewing angle, and has the added advantages of no gapsin the light field and the light field can be easily shaped, e.g., toprovide linear light intensity distributions as discussed hereinabovewith reference to FIGS. 50 and 51. Lens 460 uses refraction andreflection to capture and collimate light across a wide viewing angle.Each lens in FIG. 52 is opposite respective diode 107-109. This lensfeatures an upper portion 466 and a lower portion 467. Lower portion 467features refractive surface 463 facing the lens's respective diode andcurved internally reflective surface 461 cut horizontally by a bottomhorizontal plane 484. Upper portion 462 features refractive surface 464above the lens's respective diode and curved internally reflectivesurface 462 cut horizontally by a top horizontal plane 483.

In some embodiments, refractive surface 463 is a single-curved(x-dimension) surface. In other embodiments the surface facing the diodeis straight. Internally reflective surfaces 461 and 462 furthercollimate the light in both the x- and y-directions. When diodes 107-109are emitters, collimated light exits lens 460 through flat exit surface464. When diodes 107-109 are receivers, collimated light enters lens 460through flat exit surface 464. By cutting reflective surfaces 461 and462 horizontally with horizontal planes 483 and 484, instead ofvertically, the lens has a lower height, as explained above.

FIG. 53 shows a view from above of lens 460. Diode 108 is either an LEDor PD. FIG. 53 shows curved entry surface 463 and flat exit surface 464of lens 460. Light beams 465 are refracted at entry surface 463.

FIG. 54 shows a cutaway view from the side of light guide 460. FIG. 54shows how reflective surfaces 461 and 462 collimate light beams 465 inthe y and x directions. Surfaces 461 and 462 are curved in both the xand y directions to collimate the light in both these directions, andare cut horizontally by respective horizontal planes 484 and 483.Surfaces 461 and 462 are vertically aligned mirror images of each other.This ensures that any light reflected by one of these surfaces is alsoreflected by the other surface. Entry surface 463 and exit surface 464of lens 460 are also shown.

Lens 460 is an extremely fast lens suitable for applications requiringmuch light, yet is extremely compact. For example, in prior art systemsin which a diode is placed underneath the screen, light guides forcollimating light in the x-direction, i.e., parallel to the screensurface, employ a curved reflective surface that receives the lighttraveling downward, perpendicular to the x-direction. In prior artlenses, a double-curved reflector is cut vertically by a rear verticalplane of the light guide. The advantages of lens 460 are evident when itis compared to a prior art light guide illustrated in FIG. 55.

Reference is made to FIG. 55, which is a prior art illustration of alight guide. FIG. 55 shows diode 108 opposite a prior art collimatinglight guide 470 having a single reflector curved in two-dimensions forcollimating light from LED 108. The reflector has a height 478 which isthe sum of two heights: (a) height 476 which is determined by the heightof exit surface 474. This is the height of the incoming light channelwhich must be maintained as the light travels through light guide 470;and (b) height 472 of the parabola resulting from the fact thatdouble-curved reflector 471 is intersected by backplane 481. Themagnitude of height 472 depends on the width of the pitch betweenneighboring LEDs and the proximity of LED 108 to light wide 470. Namely,a wider viewing angle requires a greater parabolic height.

By contrast, the minimum height of lens 460 of FIGS. 52, 53, 54 and 56,is limited only to twice the height of the incoming light channel, i.e.,the sum of the heights of surfaces 463 and 464. The parabola of FIG. 55is rotated from the vertical plane to the horizontal plane in lens 460.Therefore height 472 in light guide 470 is transposed into depth 482 inthe horizontal plane in lens 460 as illustrated in FIG. 52.

Moreover, because lens 460 has two double-curved reflectors it is morepowerful, nearby twice as powerful, as light guide 470. Thus, for wideviewing angles the parabolic depth required in lens 460 is substantiallyless than the parabolic height required in light guide 470.

Reference is made to FIG. 56, which is a simplified illustration showingexample dimensions of lens 460 of FIGS. 52, 53, 54, in accordance withan embodiment of the present invention. Lens 460 can be made lessextreme with a flat entry surface and longer focal length. The distancebetween neighboring lenses can also be increased if needed. Unusualcurves used in lens 460 may result in extreme vignetting, which can becompensated with microstructures at exit surface 464.

Edge Sweep Detection

Reference is made to FIGS. 57 and 58, which are simplified illustrationsof a light guide arrangement for detecting touches and sweep gesturesperformed upon the light guide, in accordance with an embodiment of thepresent invention. FIG. 57 shows an optical touch screen with an LED-PDpair for detecting an object touching the left edge of a light guideframe, in accordance with an embodiment of the present invention. FIG.57 shows the optical touch screen of FIG. 40 where, in addition to theLEDs and PDs for detecting touch locations on the screen, an additionalLED-PD pair 106-206 is added for detecting an object touching the leftedge of light guide frame 410. LED 106 projects light beam 322 into theleft border of light guide frame 410 where light beam 322 is capturedinside a slab portion of frame 410 by total internal reflection as ittravels through. At the opposite end of this border, light beam 322 isdetected by light detector 206. The upper surface of the slab is exposedto touch by an object from outside. Such a touch absorbs a portion oflight beam 322 before it arrives at detector 206, resulting in reduceddetection at detector 206. Calculating unit 711 connected to detector206 determines that an object is touching the upper surface of the slabportion through which beam 322 passes based on this reduced lightdetection.

In certain embodiments more than one LED-PD pair is provided in order todetect movement of the object across the upper surface in a directionperpendicular to beam 322. This enables the computer to determine that asweep gesture across the border is being performed, corresponding to thesweep gesture employed by Windows 8 to open the charms bar or to togglebetween different running applications. FIG. 58 shows two emitters 106,107 that emit beams 322, 323, respectively, through light guide 411,with each beam being detected by a corresponding detector (not shown) atthe opposite end of each beam, in accordance with an embodiment of thepresent invention. FIG. 58 shows emitters 106 and 107 that emitrespective beams 322 and 323 through light guide 411. These beams areconfined inside light guide 411 by total internal reflection. Each beamis detected by a corresponding detector (not shown) at the opposite endof each beam. A sweep gesture indicated by arrow 900 across light guide411 is detected as a result of portions of internally reflected beams322 and 323 being absorbed by a finger performing the gesture as thefinger comes into contact with each beam. Furthermore, in certainembodiments, each border of frame 410 (in FIG. 57) has multiple LED-PDpairs for detecting these Windows 8 edge-related sweep gestures alongeach edge of the screen.

Reference is made to assignee's U.S. Pat. No. 8,553,014, and co-pendingU.S. patent application Ser. No. 14/016,076, both entitled OPTICAL TOUCHSCREEN USING TOTAL INTERNAL REFLECTION, which are incorporated herein intheir entirety by reference, and which describe how to project lightbeam 322 from emitter 106 into a light guide slab and determine locationof an object touching the slab's upper surface based on outputs of anopposite detector 206.

Reduced-Component Flexible Touch Screens

Discussion now turns to embodiments of the invention wherein atouchscreen has light guides along only two edges of the screen.Reference is made to FIG. 59, which is a simplified illustration of atouch screen having a row of emitters along the bottom edge of thescreen and a row of receivers along the top edge of the screen, inaccordance with an embodiment of the present invention. FIG. 59 showsscreen 803, emitter light guide 479, detector light guide 480 and lightbeams 360.

Reference is made to FIG. 60, which is a simplified illustration of thetouchscreen of FIG. 59, in accordance with an embodiment of the presentinvention. FIG. 60 shows screen 803, emitter light guide 479, detectorlight guide 480 and PCB 657.

Reference is made to FIG. 61, which is an exploded view of thetouchscreen of FIG. 59, in accordance with an embodiment of the presentinvention. This view exposes LEDs 110 and PDs 207 mounted on PCB 657underneath their respective light guides.

In another embodiment of the present invention, PCB 657 is replaced bytwo PCB strips. In this regard reference is made to FIG. 62, which is asimplified illustration of a touchscreen having a row of emitters alongthe bottom edge of the screen mounted on a first thin strip PCB and arow of receivers among the top edge of the screen mounted on a secondthin strip PCB, in accordance with an embodiment of the presentinvention. FIG. 62 shows a touchscreen embodiment with screen 803,emitter light guide 479 and detector light guide 480.

Reference is made to FIG. 63, which is an exploded view of thetouchscreen of FIG. 62, in accordance with an embodiment of the presentinvention. Thus FIG. 63 shows two PCB strips 658 and 659 on which LEDs110 and PDs 207 are mounted, respectively. As shown in FIG. 63, lightguides 479 and 480 are each made up of two parts: one above screen 803and the other below screen 803.

These embodiments of touchscreens having light guides along only twoedges of the screen enable providing optical touch functionality on aflexible screen. In this regard reference is made to FIG. 64, which is asimplified illustration of a foldable touchscreen, in accordance with anembodiment of the present invention. FIG. 64 shows foldable screen 803having emitter light guide 479 along its right edge and detector lightguide 480 along its left edge. Crease 804 down the middle of screen 803indicates where the screen can be folded in half for compact storage.The unfolded screen is touch-sensitive as long as the beams projectedfrom emitter light guide 479 arrive at detector light guide 480.Reference is made to FIG. 65 illustrating an embodiment in which boththe left and right halves of the screen have respective pairs of emitterand detector light guides 479 and 480. In this case, even when thescreen is folded along crease 804, each half of the screen is touchsensitive. For example, when the screen of FIG. 65 is folded to roughlya 90° angle so that half of the screen lies flat on a table and theother half stands upright facing the user, in the manner of an openlaptop both halves remain touch sensitive.

The determination of a touch location in these embodiments is describedwith reference to FIGS. 66-69. Reference is made to FIG. 66, which is asimplified illustration of light beams from one emitter reaching all ofthe detectors, in accordance with an embodiment of the presentinvention. FIG. 66 shows screen 803 with a row of LEDs 110 along itsbottom edge and a row of PDs 207 along its top edge. Light beams 360from one of the LEDs arrive at all of the PDs.

Reference is made to FIG. 67, which is a simplified illustration showingwhich beams from FIG. 66 are blocked by an object touching the center ofthe screen, in accordance with an embodiment of the present invention.FIG. 67 shows what happens to beams 360 when an object 910 is placed onthe screen. Thus, comparing FIGS. 67 and 66 it is evident that some ofbeams 360 are blocked by object 910 and their absence is detected atrespective ones of PDs 207.

Reference is made to FIG. 68, which is a simplified illustration showingadditional beams from other emitters that are not blocked by the objectof FIG. 67, in accordance with an embodiment of the present invention.FIG. 68 shows unblocked beams 360 from several of the LEDs.

Reference is made to FIG. 69, which is a simplified illustration showingall of the beams blocked by object 910 of FIG. 67, in accordance with anembodiment of the present invention. The area around which theintersections of these blocked beams are concentrated corresponds to thelocation of the object 910 on the screen. The two dimensional locationof the object is thus determined. Thus, 2D coordinates of a location ofa touch object correspond to the intersections of the blocked beams.Several methods for determining a touch coordinate based on aconfiguration of many intersecting beams have been described hereinabovewith regard to avoiding ghosting. Some methods process blocked beams andothers process non-blocked beams. All of these methods are alsoapplicable to the present reduced-component embodiments.

In these embodiments the resolution of the x-coordinate, namely, thecoordinate along the length of light guides 479 and 480, is higher thanthe resolution of the y-coordinate. Therefore, in some embodiments ofthe invention the touchscreen driver software distinguishes betweensituations of a single touch and situations of dual touch, ormulti-touch. In particular, in some embodiments, multi-touch gesturessuch as pinch and spread gestures are determined based only on thex-coordinates of the touches. Whereas when only one object is touchingthe screen the system determines both the x-coordinate and they-coordinate of the touch object.

Furthermore, x-coordinate detection extends the entire width of thescreen, i.e., to the edges of light guides 479 and 480, whereasy-coordinate detection is limited to an inscribed rectangle within thescreen in order to provide the multiple diagonal intersecting beamsrequired in order to determine the y-coordinate.

Circular Touch Panel

Embodiments of the subject invention relate to circular touch panels.Certain circular touch panel embodiments target small touch pads andwatches, and are roughly 40 mm in diameter. These embodiments supportmulti-touch. In certain optical touch screen implementations the channelbetween an LED and a PD consists of a wide beam of light, but for around touch surface narrow ray-like beams from LED to PD are used. Thus,these embodiments are relatively small and use tightly spacedcomponents. This enables good light coverage even though the individuallight fields are narrow.

Component Placement

Reference is made to FIGS. 70-73, which are illustrations of alternativeLED and PD layouts for a circular touch surface, in accordance withalternative embodiments of the present invention. The LEDs and PDs arepositioned so that the light coverage of the touch area is maximized,i.e., the holes in the ray grid that covers the touch area are as smallas possible.

Two different setup geometries are used: namely,

-   -   (i) alternating LED/PD, whereby every LED is positioned between        two PDs and vice versa; and    -   (ii) the LEDs and PDs are positioned on separate semicircles.

(i) Alternating LED/PD

FIG. 70 shows an arrangement of alternating LEDs and PDs with an oddnumber of LEDs. In this case, each LED is diametrically mirrored by aPD. This kind of radial symmetry generates a large circle in the centerof the touch area, mimicking a spoked wheel.

Within this circle, there is a lack of positional accuracy. Whenblocking one or more rays on one side of the center, there will alwaysbe another position diametrically opposite where the same rays can beblocked, thus generating the same signals. Therefore, within this circleit is not possible to determine on which side of the center a touch islocated.

FIG. 71 shows an arrangement of alternating LEDs and PDs with an evennumber of LEDs. In this case, each LED is diametrically mirrored byanother LED. This kind of radial symmetry generates a circular hole inthe ray pattern at the center of the touch area. No touch informationcan be generated within this circle. However, it is noted that theproblematic circle is smaller in this case.

(ii) LEDs and PDs Positioned on Separate Semicircles

In an embodiment of the present invention, breaking the radial symmetryassociated with alternating components is achieved by splitting thecircle in half and placing all of the LEDs on one side and the PDs onthe other side, where the LEDs and PDs are evenly distributed. FIG. 72shows this configuration. The PDs are arranged along the bottomsemi-circle and the LEDs are arranged along the upper semi-circle.Having the same number of LEDs and PDs provides a combination of the twoprevious layouts. There is still a central area with poor positionalaccuracy. The result is similar for an odd number of LEDs and PDs aseach LED is now always mirrored by a PD. This setup still has aleft-right symmetry associated with it. The ray pattern is improved byeliminating this symmetry. This is done, inter alia, by slightlyaltering the LED pitch and introducing an extra spacing of half a pitchbetween every third LED. This also decreases the number of LEDs. Thisarrangement of LEDs and PDs is illustrated in FIGS. 75 and 76. Theresulting pattern of detection beams is shown in FIGS. 73 and 77.

Light Guide Design

Reference is made to FIG. 74, which is an illustration of a light guidefor a circular touch surface, in accordance with an embodiment of thepresent invention. The left pane in FIG. 74 is a cross-section of thelight guide. The many-to-many mapping of LEDs to PDs requires a largeangular spread of light, which is provided by the LEDs and PDs. A smallfocusing effect in height is introduced in the folding mirror closest tothe components, as illustrated by the arc along the bottom right cornerof the cross-section shown in the left pane in FIG. 74. Other than that,the plastic light guide serves as a redirecting component to get thelight across the touch area with an arrangement of mirror surfaces usingtotal internal reflection. The curved mirror is slightly defocussed,roughly filling its corresponding diode. No draft angles are present inembodiments using a milled light guide. A consequence of the straightbezel is that the unit works when fully submerged in water, providedthat it is watertight. The cross section shown in the left pane of FIG.74 is rotated 360° to create a circularly symmetric light guide. Thebezel height is 1 mm and the touch area diameter is 40 mm.

Reference is made to FIG. 75, which is an illustration of a PCB layoutfor a circular touch surface, in accordance with an embodiment of thepresent invention. FIG. 75 shows different numbers of LEDs and PDs;namely, 11 LEDs IR1-IR11 along the upper half of PCB 661, and 12 PDsPD1-PD12 along the bottom half of PCB 661. Whereas the PDs are evenlyspaced, with an angular displacement of 15° between each detector andits neighbor, the LEDs are divided into four groups with an angulardisplacement of 14° within each group and 21° (1.5*14°) between thegroups.

In the interior of PCB 661 a plurality of electronic components isprovided for the proper function of the touch sensitive surface, interalia, controller 715, which selectively activates and deactivates theLEDs and PDs.

Reference is made to FIG. 76, which is an illustration of light beamsemitted by one LED detected by a plurality of PDs surrounding a circulartouch surface, in accordance with an embodiment of the presentinvention. FIG. 76 shows a range of detected beams 332 emitted by LEDIR1. As explained above, tables measuring detected intensities ofnon-blocked beams are prepared in order to examine which beams are notsufficiently detectable and in order to determine a threshold value,e.g., half of the expected intensity of the non-blocked beam, for theusable beams. Thus, in practice, not all beams 332 are used to detecttouches by the system. For example, the IR1-PD12 beam is not used as itis detected even when the entire circular input surface is covered by anopaque object.

Reference is made to FIG. 77, which is an illustration of a network ofintersecting light beams used in a circular touch surface, in accordancewith an embodiment of the present invention. FIG. 77 shows all of theused beams encircled by light guide 424 in a circular touch systemaccording to the present invention.

Reference is made to FIG. 78, which is a simplified illustration of acircular touch surface sensor, in accordance with an embodiment of thepresent invention. FIG. 78 shows a 3D model of a circular touch panelaccording to the present invention. A touch plate 810 is surrounded by alight guide 424. The light beams 332, shown in FIGS. 76 and 77, areprojected through light guide 424. Also shown in FIG. 78 are top andbottom covers 811 and 812 and a connecting wire 912 for a hapticvibrator explained below.

Reference is made to FIG. 79, which is an illustration of the componentsused to assemble a circular touch surface, in accordance with anembodiment of the present invention. FIG. 79 shows the main componentsin an exemplary circular touch sensor according to the presentinvention, namely, front cover 811, back cover 812, touch plate 810,light guide 424, PCB 661, screws 911, haptic vibrator 913 and its cable912.

Reference is made to FIG. 80, which is an exploded view of the circulartouch surface of FIG. 78, in accordance with an embodiment of thepresent invention. Front and back covers 811, 812 encase touch plate810, light guide 424 and PCB 661. Also shown are screws 911, hapticvibrator 913 and associated cable 912 that connects the device to a hostsystem. Haptic vibrator 913 provides tactile sensory feedback throughtouch plate 810 in response to touch inputs detected thereon.

Reference is made to FIG. 81, which is a cutaway view of the circulartouch surface of FIG. 78, in accordance with an embodiment of thepresent invention. Like reference numerals in FIGS. 80 and 81 indicatethe same elements. The upper rim of light guide 424 extends above touchplate 810 forming a bezel.

Reference is made to FIG. 82, which is a simplified illustration of alight guide for the circular touch surface of FIG. 78, in accordancewith an embodiment of the present invention. FIG. 82 shows light guide424 with two reflective surfaces for redirecting the light beams. Alight shield 421 along the inner perimeter of circular light guide 424prevents stray light from above from hitting the light detectors.

Reference is made to FIGS. 83 and 84, which illustrations of paths oflight beams used in a circular touch surface, in accordance with anembodiment of the present invention. FIG. 83 shows the reflectiveproperties of light guide 424. LED 110 and PD 220 are shown facingoutward of circular light guide 424. Light beam 333 from LED 110 isprojected outward into light guide 424. Two reflective facets redirectbeam 333 over and across touch plate 810. Similar reflective facets atthe opposite edge of plate 810 redirect beam 333 onto PD 220. Lightguide 424 is optimized to spread the light such that each LED hasdetectable beams arriving at all, or at least at many, of the PDs.

FIG. 84 shows beams 332 from LED 111, at the center of the arc ofemitters, projected onto all of the PDs. In FIG. 84, the upper half ofthe circular touch area is lined with 12 PDs, and the lower half of thecircular touch area is lined with 11 LEDs. The multi-tiered arrangementof LEDs, whereby groups of LEDs have a different angular displacementthan neighboring LEDs within a group is described above and illustratedin FIGS. 75 and 76.

In the foregoing specification, the invention has been described withreference to specific exemplary embodiments thereof. It will, however,be evident that various modifications and changes may be made to thespecific exemplary embodiments without departing from the broader spiritand scope of the invention. Accordingly, the specification and drawingsare to be regarded in an illustrative rather than a restrictive sense.

1-11. (canceled)
 12. A method for calculating multiple touch locationson a screen comprising: activating a plurality of light emitters andlight detectors around the perimeter of a screen, each emitter-detectorpair corresponding to a light path crossing the screen, wherein some ofthe light paths are blocked when one or more objects touch the screen;providing a look-up table, listing, for each cell from a plurality ofcells, those light paths that traverse that cell when no object istouching the screen, wherein the plurality of cells comprises aplurality of sub-areas that form a partition of the screen; for eachcell: accessing the look-up table to identify those light paths thattraverse that cell; and determining whether the thus-identified lightpaths are blocked during said activating and, if affirmative,recognizing that cell as being a touched cell; and combining adjacenttouched cells into a common touch location, thereby calculating one ormore touch locations wherein each touch location is a combination of oneor more constituent touched cells.
 13. The method of claim 12, whereinthe cells are of different sizes.
 14. The method of claim 12, whereineach cell surrounds a point of intersection between two light paths. 15.The method of claim 12, further comprising calculating an area for eachtouch location according to the sum of the areas of that touchlocation's constituent cells.
 16. The method of claim 15, furthercomprising: providing a range of values for the area of a touchlocation; and validating those touch locations whose calculated area iswithin the range.
 17. The method of claim 16, further comprisingassociating each touch location whose calculated area exceeds the range,with a plurality of objects touching the screen at that location.
 18. Amethod for calculating multiple touch locations on a screen comprising:activating a plurality of light emitters and light detectors around theperimeter of a screen, each emitter-detector pair corresponding to alight path crossing the screen, wherein some of the light paths areblocked when one or more objects touch the screen; providing a look-uptable, listing, for each light path, those cells from a plurality ofcells, that are traversed by that light path when no object is touchingthe screen, wherein the plurality of cells comprises a plurality ofsub-areas that form a partition of the screen; for each light path thatis not blocked during said activating, accessing the look-up table toidentify those cells that the identified light path traverses, andrecognizing the thus-identified cells as being untouched calls;classifying those cells that are not recognized as being untouchedcells, as being touched cells; and combining adjacent touched cells intoa common touch location, thereby calculating one or more touch locationswherein each touch location is a combination of one or more constituentcells.
 19. The method of claim 18, wherein the cells are of differentsizes.
 20. The method of claim 18, wherein each cell surrounds a pointof intersection between two light paths.
 21. The method of claim 18,further comprising calculating an area of each touch location accordingto the sum of the areas of that touch location's constituent cells. 22.The method of claim 21, further comprising: providing a range of valuesfor the area of a touch location; and validating those touch locationswhose calculated area is within the range.
 23. The method of claim 22,further comprising associating each touch location whose calculated areaexceeds the range with a plurality of objects touching the screen atthat location.